On Wed, 10 Apr 2024 16:41:43 -0500 Rob Herring <robh@xxxxxxxxxx> wrote: > On Tue, Mar 19, 2024 at 11:34 AM Herve Codina <herve.codina@xxxxxxxxxxx> wrote: > > > > Hi Bjorn, > > > > On Tue, 19 Mar 2024 10:25:13 -0500 > > Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > > > > [+cc Krzysztof] > > > > > > On Fri, Dec 15, 2023 at 02:52:07PM +0100, Herve Codina wrote: > > > > On Mon, 4 Dec 2023 07:59:09 -0600 > > > > Rob Herring <robh@xxxxxxxxxx> wrote: > > > > > On Mon, Dec 4, 2023 at 6:43 AM Herve Codina <herve.codina@xxxxxxxxxxx> wrote: > > > > > > On Fri, 1 Dec 2023 16:26:45 -0600 > > > > > > Rob Herring <robh@xxxxxxxxxx> wrote: > > > > > > > On Thu, Nov 30, 2023 at 10:57 AM Herve Codina <herve.codina@xxxxxxxxxxx> wrote: > > > > > > > ... > > > > > > > > > > --- a/drivers/pci/of.c > > > > > > > +++ b/drivers/pci/of.c > > > > > > > @@ -31,6 +31,8 @@ int pci_set_of_node(struct pci_dev *dev) > > > > > > > return 0; > > > > > > > > > > > > > > node = of_pci_find_child_device(dev->bus->dev.of_node, dev->devfn); > > > > > > > + if (!node && pci_is_bridge(dev)) > > > > > > > + of_pci_make_dev_node(dev); > > > > > > > if (!node) > > > > > > > return 0; > > > > > > > > > > > > Maybe it is too early. > > > > > > of_pci_make_dev_node() creates a node and fills some properties based on > > > > > > some already set values available in the PCI device such as its struct resource > > > > > > values. > > > > > > We need to have some values set by the PCI infra in order to create our DT node > > > > > > with correct values. > > > > > > > > > > Indeed, that's probably the issue I'm having. In that case, > > > > > DECLARE_PCI_FIXUP_HEADER should work. That's later, but still before > > > > > device_add(). > > > > > > > > > > I think modifying sysfs after device_add() is going to race with > > > > > userspace. Userspace is notified of a new device, and then the of_node > > > > > link may or may not be there when it reads sysfs. Also, not sure if > > > > > we'll need DT modaliases with PCI devices, but they won't work if the > > > > > DT node is not set before device_add(). > > > > > > > > DECLARE_PCI_FIXUP_HEADER is too early as well as doing the DT node creation > > > > just before the device_add() call. > > > > Indeed, in order to fill the DT properties, resources need to be assigned > > > > (needed for the 'ranges' property used for addresses translation). > > > > The resources assignment is done after the call to device_add(). > > > > > > Do we need to know the actual address *value* before creating the > > > sysfs file, or is it enough to know that the file should *exist*, even > > > if the value may be changed later? > > > > I think, the problematic file is 'of_node'. > > This file is a symlink present in the device directory pointing to the > > node in a device-tree subdir. > > > > How can we create this of_node symlink without having the device-tree > > subdir available ? > > > > > > > > > Some PCI sysfs files are already created after adding the device by the > > > > pci_create_sysfs_dev_files() call: > > > > https://elixir.bootlin.com/linux/v6.6/source/drivers/pci/bus.c#L347 > > > > > > > > Is it really an issue to add the of_node link to sysfs on an already > > > > present device ? > > > > > > Yes, I think this would be an issue. We've been trying to get rid of > > > pci_create_sysfs_dev_files() altogether because there's a long history > > > of race issues related to it: > > > > > > https://lore.kernel.org/r/1271099285.9831.13.camel@localhost/ WARNING: at fs/sysfs/dir.c:451 sysfs_add_one: sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:01.0/slot' > > > https://lore.kernel.org/r/19461.26166.427857.612983@xxxxxxxxxxxxxxxxxxx/ [2.6.35-rc1 regression] sysfs: cannot create duplicate filename ... XVR-600 related? > > > https://lore.kernel.org/r/20200716110423.xtfyb3n6tn5ixedh@pali/ PCI: Race condition in pci_create_sysfs_dev_files > > > https://lore.kernel.org/r/m3eebg9puj.fsf@xxxxxxxxxxx/ PCI: Race condition in pci_create_sysfs_dev_files (can't boot) > > > https://bugzilla.kernel.org/show_bug.cgi?id=215515 sysfs: cannot create duplicate filename '.../0000:e0' > > > > > > And several previous attempts to fix them: > > > > > > https://lore.kernel.org/r/4469eba2-188b-aab7-07d1-5c77313fc42f@xxxxxxxxx/ Guard pci_create_sysfs_dev_files with atomic value > > > https://lore.kernel.org/r/20230316103036.1837869-1-alexander.stein@xxxxxxxxxxxxxxx PCI/sysfs: get rid of pci_sysfs_init late_initcall > > > https://lore.kernel.org/r/1702093576-30405-1-git-send-email-ssengar@xxxxxxxxxxxxxxxxxxx/ PCI/sysfs: Fix race in pci sysfs creation > > > > > > > I am not sure we are facing in the same kind of issues. > > The ones you mentioned are related to some sysfs duplication. > > In the of_node case, the issue (if any) is that the symlink will be created > > after the other device's file. Not sure that it can lead to some file > > duplication. > > Again, if you notify userspace and it wants to make some decisions > based on of_node, then it has to be there when the notification > happens. As Greg says frequently, you've raced with userspace and > lost. > > I imagine Bjorn won't like it, but may we need another fixup point? > > Rob I'am not sure that a fixup point can fix the issue. In order to have the of_node available before the notification, we need to a have the of_node set and filled before the device_add() call. In order to create the 'ranges' property in the DT node, we need PCI resources computed. These resources are computed after the device_add() call. Hervé
